1. Field of the Invention
The present invention relates to a keyswitch structure, and particularly relates to a keyswitch structure including a slender key cap and an integral balance structure for a key with a short press stroke.
2. Description of Related Art
Keyswitch structures are widely utilized in many devices, such as computers, telephones, cell phones or operational panels of machines, for inputting data or actuating such devices. Efforts have been made to improve the keyswitch structure so as to have a more reliable operation.
In order to distribute the force of the keyswitch, the keyswitch usually has a scissors structure arranged under a key cap of the keyswitch. No matter how the force is acted on a lateral edge or a lateral side of the keyswitch, the force can be averagely distributed over the whole keyswitch for user to press the keyswitch easily. A portable keyswitch has a strict space limitation in a notebook or a foldable keyswitch, and usually has a scissors structure for convenient operation.
Moreover, with regard to a wider keyswitch such as space key, in order to distribute the force on the lateral side, the key cap usually has a metal balance rod arranged under the key cap. The balance rod is used to balance the two lateral forces for preventing the key from swinging and being wedged.
U.S. Pat. No. 6,726,093 B2 is published on Apr. 27, 2004, and discloses a key structure having a scissors frame and a balance rod. FIG. 1 shows a perspective, exploded view of the key structure of the related art. The key structure includes a bottom seat 4a, a key cap 1a arranged on the bottom seat 4a, a balance rod 3a arranged between the key cap 1a and the bottom seat 4a, and a scissors structure 2a arranged between the bottom seat 4a and the key cap 1a. The balance rod 3a has a first side 31a connected to a sliding groove 11a that is formed on a bottom portion of the key cap 1a, and a second side 32a connected to a guiding groove 43a of the bottom seat 4a. The key cap 1a can be upwardly and downwardly moved relative to the bottom seat 4a by the scissors structure 2a and the balance rod 3a. 
However, the key structure is difficult to adapt to a key under strict space limitations. First, the keyswitch structure cannot adapt to a slender key cap, because the key cap needs a larger area for the scissors structure 2a and the balance rod 3a to be arranged on the bottom portion thereof. The key structure is difficult to adapt to a slender key for assembly. Besides, the key structure is difficult to adapt to a key with a short press stroke like 0.5 mm to 2 mm for assembly, because the key structure has a longer press stroke. The whole height of the key is increased by the scissors structure 2a and the balance rod 3a. Moreover, the key structure has too many components and a complex assembly.